Esters of perfluoroacrylic acid, CF.sub.2 .dbd.CFCOOH, are useful for making copolymers containing --COOR side chains, which may be converted to --COOH or --COO.sup.- Na.sup.+ groups for uses such as membranes for electrolysis, particularly the electrolysis of aqueous NaCl.
Prior processes for the synthesis of perfluoroacrylic acid esters include:
(1) a process wherein trichlorofluoromethane is added to 1,2-dichlorodifluoroethylene or carbon tetrachloride is added to chlorotrifluoroethylene to obtain 1,1,2-trifluoropentachloropropane, which is then oxidized and esterified to form a 2,3-dichlorotrifluoropropionic acid ester, followed by dechlorination of the ester; (2) a process wherein bromine is added to chlorotrifluoroethylene to obtain 1,2-dibromo-1-chlorotrifluoroethylene, which is then subjected to an addition reaction with propylene, followed by dehydrobromination to obtain 5-bromo-4-chloro-4,5,5-trifluoropentene-2 (CF.sub.2 BrCFClCH.dbd.CHCH.sub.3), which is then oxidized and esterified to form a 3-bromo-2-chlorotrifluoropropionic acid ester, which is in turn dehalogenated; and (3) a process wherein chlorotrifluoroethylene is subjected to an addition reaction with hydrogen bromide, followed by dehalogenation to obtain trifluoroethylene, which is then subjected to an addition reaction with ICl, followed by dehydrochlorination to obtain trifluoroiodoethylene, which is then reacted with metallic magnesium in ether to form an organomagnesium intermediate, which is in turn reacted with carbon dioxide, followed by hydrolysis to obtain perfluoroacrylic acid, which is then esterified.
However, these processes have drawbacks in that they require cumbersome operations and expensive reactants and the total yield of the desired substance is extremely low.
An object of the present invention is to prepare CF.sub.2 .dbd.CFCOOR by a high-yield process from readily available starting materials.
Another object is to prepare CF.sub.2 .dbd.CFCOOR by a process which requires a minimum of purification of intermediate products.